MTN REALLY BAD SERVICE

I cannot get to cancel my contract. The term has passed, and I would like to migrate the numbers to pay as you go. I phone, but hold on for an operator for more than 40min at a time. Sent emails to retention and customer care as advised online, but every month I get a new invoice with both numbers still on it. This is absolutely ridiculous. I will never ever in my life get an MTN contract again and will not recommend this provider to anyone.